As agencies control invasive species to protect diversity, some worry about side effects

Aug 9, 2013

Each year, millions of dollars are spent controlling invasive species in Wyoming. Just about every agency you can think of is involved – from local weed and pest districts, to the Department of Game and Fish, and even the Bureau of Land Management. Many people see their efforts as an important way to protect Wyoming’s diversity. But others worry that removing invasives could sometimes do more harm than good. Wyoming Public Radio’s Willow Belden reports.

Dee Hillberry removed Russian Olives from his riverbank, opening up the view and creating more usable pasture. Across the river, a Russian Olive grove remains.
Credit Willow Belden

WILLOW BELDEN: Dee Hillberry owns a farm just outside Thermopolis. His porch overlooks grassy fields and the Bighorn River. But it didn’t always look like this.

DEE HILLBERRY:  Three years ago, standing in this spot, you could not see the river.

BELDEN: That’s because a type of tree called Russian Olives had taken over the riverbanks and many of the surrounding fields. That blocked the view, and meant there was less and less land available for growing crops. Plus, unwanted animals started showing up, like raccoons and skunks.

HILLBERRY: One year, between the raccoons and the white-tailed deer, we lost 38 percent of our corn crop.

BELDEN:  Russian Olives are not native to Wyoming, but they used to be seen as a good thing. In the 1800s, people planted them as ornamental trees, and to block the wind. But then they started spreading, fast. Amy Anderson with the Wyoming Game and Fish Department says that’s when they became a problem.

ANDERSON:   They tend to use more water than native species. They create assemblages that make it very difficult to use the river, either recreationally or in agriculture. And they spread really quickly and choke out our native species.

BELDEN: They also change the salt content of the soil. All of that means the ecosystem loses diversity. And Anderson says that makes those areas less attractive to certain types of wildlife, including sage grouse. Those are some of the reasons she’s been coordinating a massive effort to remove Russian Olives, and another invasive species called salt cedar, in the Bighorn Basin. So far, about 15,000 acres have been cleared.

But some think removal is misguided. Bruce Ostermann is one of them.

BRUCE OSTERMANN: I think it’s a heck of a good tree, and it grows where nothing else will grow.

BELDEN: Ostermann owns property just down the river from Dee Hillberry’s farm. His riverbank is shaded by a dense grove of Russian Olives. But across the river, the landscape is bare. The invasive trees were cut down this spring and stacked into huge brush piles. Ostermann says the lack of shade seems to be warming the river and affecting fish.

Some landowners worry that without the root systems from the Russian Olives, river banks like this one could erode.
Credit Willow Belden

OSTERMANN: Most of the time we’re worried about deforestation, and here we’re deforesting the entire Bighorn Basin.

BELDEN: Anderson and her team are trying to replant native species, like cottonwoods and willows. But getting the natives to regrow is not always successful.

Russian Olives are just one of many invasive species that Wyoming is trying to control. There are dozens of other plants and some non-native fish that are also being targeted. Sometimes it’s because they choke out important natives. Sometimes they increase the risk of wildfires. Other times they’re toxic to livestock. Removing the invaders can help lessen those negative impacts. One project was so successful that it helped keep a rare type of trout off the Endangered Species List.

But some ecologists urge caution.

DOV SAX: Not all non-native species are a net detriment, and some of them may provide benefits that in some cases outweigh the costs.

BELDEN: Dov Sax is an ecologist at Brown University who studies how species invasions impact native ecosystems. He points out that honey bees are not native to the U.S. but they provide important services. Similarly, some non-native plants can clean pollutants out of wetlands. Even the salt cedar that Wyoming is removing has been useful in the southwestern U.S. to provide habitat for endangered bird species. So Sax says it’s not always worth spending a lot of money to get rid of something just because it’s non-native.

SAX: Especially if it’s already established in an area and would be expensive to remove or try to remove, the question is: “Is it worth spending money to try to do this? And if we were to be successful, would we have net outcomes that were good for conservation as a consequence, or might there actually be net costs?”

BELDEN: In the end, decisions regarding invasive species management often come down to value judgments. Brian Mealor with the University of Wyoming Extension says it’s often the ag industry that drives initiatives to remove invasive species. But he says in this case, environmental advocates are often on board.

BRIAN MEALOR:  And I think oftentimes one of the reasons why people can get behind invasive species management efforts is because it can benefit all of those interests. It’s not really an “either-or” situation.

BELDEN: For Wyoming Public Radio, I’m Willow Belden.